Signal-translating system for television receivers



B. D. n oUGHLlN r2,678,388

2 Sheets-Sheet 1 May 11; 1954 SIGNAL-TRANSLATING SYSTEM FOR TELEVISIONAREICEHVERSf Filed Aug. 14, 1950 May 11, 1954 B, D, LQUGHLlN 2,678,388

SIGNAL-TRANSLATING SYSTEM FOR TELVISION RECEIVERS y Filed Aug. 14, v19502 Sheets-Sheet 2 Patented May 11, 1954 SIGNAL-TRANSLATING SYSTEM FORTELEVISION RECEIVERS Bernard D. Loughlin, Lynbrook, N. Y., assignor toHazeltine Research, Inc., Chicago, Ill., a corporation of IllinoisApplication August 14, 1950, Serial No. 179,121

20 Claims. (Cl. Z50-27) GENERAL The present invention relates totransientmodifying electrical signal-translating systems for televisionreceivers and, particularly, to such systems which are effective, whiletranslating an applied television signal including unidirectionaltransients, to develop a television output signal including modifiedtransients which may correspond aproxirnately to but have slopes muchsteeper than those of the transients appearing in the applied signal.The term unidirectional transient, as employed in the specication andclaims, is intended to denote a sudden change in the amplitude of asignal such as may occur in the video-frequency portion of a detectedtelevision signal between two amplitude levels thereof.Transient-modifying electrical signal-translating systems of the typeunder consideration have particular utility in television receivers forimproving the sharpness of the images produced thereby and, hence, willbe described in that environment.

There presently exists the belief that much of the eye fatigue anddispleasure often experienced by individuals viewing the image orpicture produced by a television receiver is due to insucient sharpnessof the picture rather than to inadequate detail or resolution. Bysharpness ofthe reproduced picture is meant the rate of change ofbrightness thereof with space, that is, sharpness is related to theappearance of a distinct edge between two areas of different brightness.The lack of sharpness of the picture being watched is believed to causethe eye muscles of an observer to function in such a manner as toattempt to produce a sharper or better focused image on the retina ofthe eye. When the picture being viewed has insuflicient sharpness, theremay result a continued subconscious action on the part of the observerto focus his eyes in the manner just mentioned, thus causing eyefatigue. Gn the other hand, inadequate detail in the viewed picture isbelieved merely too iniuence the recognition of ne detailed objects. lthas been recognized that the above-mentioned distress experienced bythose observing television entertainment will be further aggravated asthe use of television image-reproducing devices with larger displayareas becomes more widespread. This is because one observing a largertelevision picture is more likely to sit at such a Viewing distance fromthe television screen that the picture will subtend a larger angle, thusmaking the grain or spoty structure of the picture more visible. Thisfollows since an observer is able more easily to resolve the grain orspot structure of a larger picture. Since the present trend intelevision receivers is toward the use of larger image-reproducingdevices therein, the problem of providing greater sharpness intelevision pictures is assuming greater importance.

In a complete television system including both the transmitter and thereceiver, there are one or more factors which are instrumental incausing the bandwidth of a television signal translated thereby to belimited. Band-width limitation occurs in the scanning spot of the cameraor picture tube at th-e transmitter, in the signal-translating channelsof both the transmitter-and the receiver, and in the scanning spot ofthe imagereproducing device of the receiver. The limitation on bandwidthimparts a corresponding limitation on the detail or resolution of thepicture produced by the receiver of the television system. Inconventional television receivers, the relatively limited bandwidth ofthe signal-translating channels thereof undesirably places a limitationon the sharpness oi the reproduced picture. Heretofore it had been theopinion of workers in the television art that the resulting limitationplaced on the sharpness of the reproduced picture was a fundamental one.Experience has indicated that while band-width limitation mayfundamentally place a restriction on the sharpness of the picturereproduced by a television apparatus having a linear characteristic,this band-width limitation is not a necessary restriction in atelevision apparatus which eiectively has a nonlinear characteristic.

It recently has been conclusively demonstrated that the sharpness of thereproduced television picture need not be limited by the bandwidth ofthe television signal-translating circuits and the scanning spotsmentioned above, thus disproving the belief formerly held by thoseskilled in the art. 'In prior television receivers, however, the

Vreduced bandwidth afforded by the electrical circuits and the scanningspots inherently prevented the translation of the highest frequencycomponents of an applied television signal, thus prolonging the timerequired for a transient to pass from one amplitude level to another.This resulted in a degraded transient having' a gradual slope ratherthan a steep one, thus causing a general laclr of sharpness in thereproduced picture. It has been established that the reduced bandwidthof the signal-translating stages ofv television apparatus, such as atelevision receiver, is eective to control only the permissible minimumtime separation between two successive unidirectional transients butneed not control the permissible steepness of a transient.

Although it is ordinarily desirable to employ transient-modifyingelectrical signal-translating systems in accordance with the presentinvention in connection with television receivers having pass-bandcharacteristics such as are ordinarily employed in receivers availabletoday, it may be desirable for many applications, such as in lowcostreceivers having relatively inexpensive cir-- cuits characterized bytheir narrow pass-band characteristics, to utilize thereintransient-modiiying signal-translating systems which enable suchreceivers to produce pictures having a sharpness comparable to that ofpictures produced by conventional television receivers. Thus, relativelyinexpensive television receivers capable of producing a satisfactoryimage can be made available to a large group of the public to whomtelevision receivers heretofore were unavailable because of the pricethereof.

It is an object of the invention, therefore, to provide a new andimproved signal-translating system for a television receiver whichavoids one or more of the above--mentioned disadvantages and limitationsresulting from the use of prior translating systems in televisionreceivers.

It is another object of the invention to provide a relatively simplesignal-translating system for use in a television receiver to enable thereceiver to produce a picture which is considerably sharper than hasheretofore been obtainable.

It is a further object of the invention to provide a new and improvedsignal-translating system for use in a television receiver to reduce theeye fatigue and displeasure ordinarily experienced by some observers ofthe television pictures produced by the receiver.

It is yet another object of the invention to provide a new and improvedtransient-modifying signal-translating system for use in a televisionreceiver provided with an image-reproducing system having a relativelylarge display area to produce a sharp picture thereon.

It is an additional object of the invention to provide atransient-modifying electrical signaltranslating system for a televisionreceiver having a narrow pass-band characteristic to enable thatreceiver to develop a television image having a sharpness comparable tothat of the image produced by a conventional television receiver havinga much wider band-pass characteristic.

In accordance with a particular form of the invention, atransient-modifying electrical signaltranslating system for a televisionreceiver for translating a television picture signal which may includeunidirectional transients comprises a television signal-translatingchannel normally having a substantially linear signal-translatingcharacteristic for an applied television picture signal. Thesignal-translating system also includes control-circuit means coupled incircuit with the channel for developing a control effect related to aderivative of the transient. The signal-translating system furtherincludes means responsive to the aforesaid control effect for modifyingthe signal-translating characteristic of the channel within a shortinterval after the initiation of the transient, whereby the outputsignal of the channel approximately corresponds to the applied signalwith modified transients.

The term derivativa as employed throughout the specication and claims,is intended to denote any signal having the general Wave form of aderivative. Broadly speaking, a derivative of an applied signal is asignal related to a changing characteristic of that applied signal, thatis, a signal which has zero value when that applied signal is constantin magnitude at any particular amplitude level and has some magnitudeother than zero when the applied signal has a transient between twoamplitude levels. Thus, the broad term derivativef as used in thespecification and claims, is not necessarily a simple nrst, second, orthird derivative but may include nonlinear functions of simplederivatives, cross products between simple derivatives, time-diierencesignals, or any other vfunctions producing signals of the general formdescribed above.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1 is a circuit diagram, partlyschematic, of a complete television receiver including atransient-modifying electrical signal-translating system in accordancewith a particular form of the present invention; Fig. 2 is a graphutilized in explaining the operation of the transient-modifyingelectrical signal-translating system of the Fig. 1 receiver; Fig. 3 is aschematic circuit diagram of another form of the signal-translatingsystem in accordance with the invention; Fig. 4 representsdiagrammatically a further modification of a transientmodifyingsignal-translating system for a television receiver; Fig. 5 yis aschematic circuit diagram of a signal-translating system correspondingto that represented in Fig. 4; and Fig. 6 is a graph utilized inexplaining the operation of the system of Fig. 5.

Description of Fig. 1 recever Referring now more particularly to Fig. lof the drawings, the television receiver there represented comprises areceiver of the superheterodyne type including an antenna system it, i icoupled to a radio-frequency amplifier l2 of one or more stages. Thereis coupled to the latter unit in cascade, and in the order named, anoscillator-modulator I3, an intermediate-frequency amplier Ill of one ormore stages, a detector and automatic-gain-control or A. G. C. supply I5having a pair of output terminals 4i), et, a videofrequency amplifier lt of one or more stages and including output terminals 30, 323 connectedto a low-impedance output circuit thereof such as to the cathoderesistor of a cathode-follower videofrequency amplifier stage, atransient-modifying electrical signal-translating system if, and acathode-ray tube image-reproducing device i8 of conventionalconstruction provided with input terminals 3|, 3l and the usualline-frequency and field-frequency scanning coils (not shown) fordefiecting the cathode-ray beam in two directions normal to each other.The A. G. C. supply circuit l5 is connected to the input circuits of oneor more of the stages of units i2, I3 and I4 by a control-circuitconductor 25. Connected to the output terminals of theintermediate-frequency amplifier Hl is a conventional sound-reproducingsystem 23 which comprises the usual amplifiers, a frequency detector,and a loudspeaker.

An output circuit including the terminals 30, 38 of the video-frequencyamplifier I6 is coupled to the input Circuit of a line-frequencygenerator vil and a field-frequency generator 22 through asynchronizing-signal amplifier and separator I9 and anmtersynchroniZing-signal separator 20. The output circuits of thegenerators 2l and 22 vare coupled in a yconventional manner to thescanning coils of the image-reproducing device iS. The units ill-23,inclusive, with the exception of the transient-modifyingelectrical'signaltranslating system il which is constructed inaccordance with the present invention and will be described vin detailhereinafter, may be of conventional construction and operation so that adetailed description and explanation of the operation thereof areunnecessary herein.

General operation of Fig. 1 receiver lConsidering brieiiy, however, thegeneral operation of the above-described receiver as a whole, televisionsignals intercepted by the antenna system l0, Il are selected andamplified in the radio-frequency amplier l2 and are supplied to theoscillator-modulator i3, wherein they are converted intointermediate-frequency signals. The latter in turn are selectivelyamplified in the intermediate-frequency amplier i4 and are delivered tothe detector and automatic-gain-control supply i5. The modulationcomponents of the signal are derived by the detector l5 and are suppliedto the video-frequency amplifier lES wherein they are amplified and fromwhich they are supplied to the transient-modifying electricalsignal-translating system il and then to the input circuit of theimage-reproducing device IB. The transient-modifying operation of unitIl will be explained in detail hereinafter. A control voltage derived bythe automatic-gain-control supply of unit I5 is applied as anautomaticamplication-control bias to the gain-control circuits of unitsi2, i3 and lli to maintain a signal input to the detector of unit l5within a relatively narrow range for a Wide range of received signalintensities.

Unit IS selects the synchronizing signals from the other modulationcomponents of the composite video-frequency signal applied thereto fromthe video-frequency amplier i6. The linesynchronizing andfield-synchronizing signals derived by the separator i9 are separatedfrom each other by unit 2G and are then supplied to individual ones ofthe generators 2| and 22 to i synchronize the operation thereof. Anelectron beam is producd by the cathode-ray image-reproducing device I8and the intensity of this beam is controlled in accordance with thevideo-frequency and control voltages impressed on the brilliancy-controlelectrode by the terminals 3|, 3l. Saw-tooth current waves are generatedin the line-frequency and the held-frequency generators 2| and 22,respectively, and are applied to the scanning coils of unit I8 toproduce scanning fields, thereby to deflect the cathode-ray beam of thatunit in two directions normal to each other to trace a rectilinearscanning pattern on the screen of the tube and thereby reconstruct thetranslated picture.

The audio-frequency modulation components of the received signal arederived in a conventional manner by the sound-reproducing system 23 andare applied to the loudspeaker thereof and converted to sound.

Description of transient-modifying signal-trans- Zatng system of Fig. 1

Referring now more particularly to the portion of the receiver embodyingthe present invention,

mal-translating channel.

the transient-modifying electrical signal-translating system fortranslating a television signal which may include `unidirectionaltransients comprises a television signal-translating channel normallyhaving a substantially linear signal-translating characteristic for anapplied television picture signal. As represented in Fig. 1, thischannel comprises `the circuit portion of unit l1 between the outputterminals 30, Sil of the videofrequency amplifier I6 and the inputterminals 3i lof the image-reproducing device 13. However, thissignal-translating channel may be considered to include suitableamplifier stages such vas the video-frequency vamplifier IB or evenapparatus such as the units .I2-t5, inclusive. Particularly whenconsidering the signal-translating channel from the last-mentionedstandpoint, it maybe regarded as having a pass-band characteristiccomparable to that of the picture-signal translating channel of aconventional television receiver. This channel includes abridgerectifier circuit having two diagonally disposed terminals 2B, 26thereof `conductively connected to the high-potential ones of theterminals 3B, 3 and 3i, 3i. This bridge-rectifier circuit includes apair of parallel-connected paths, the rst path including rectier devices2l and 28 and the second path including rectier devices 32 and 33. Therectier devices may be of the contact, crystal. or the thermionic typeand, for convenience,

have been represented as diodes. The anodes of the diodes 2l and 28 areconnected together and the individual cathodes thereof are connected toopposite ones of the terminals 2S, 25. The diodes 32 Aand `33 areconnected to the terminals 25, 26 in Aa kmanner similar to thefirst-mentioned diodes but with opposite polarity. An energy-storagedevice comprising a condenser 3d is connected across the outputterminals of the described sig- An energizing source such as a battery35 is connected with such polarity to the remaining pair of diagonallydisposed terminals 3'l, 31 of the bridge-rectiiier circuit through apair of resistors 36, 36 as to maintain the diodes 2l, 2B, 32 and 33 ina normally vconductive condition.

The transient-modifying electrical signaltranslating system alsoincludes control-circuit lmeans coupled in circuit with the describedsignal-translating channel for developing a control effect related to aderivative of a transient. This means includes a differentiating circuitlil of well-known construction coupled to an output `circuit of thevideo-frequency amplifier I6 for developing a derivative of the signalapplied thereto, in particular the rst derivative of a transient of thesignal, and a full-wave rectifier e2, which is coupled to the outputcircuit of the differentiating unit 4| for developing a signalcorresponding to the absolute magnitude of the derivative signal. Thecontrol circuit further includes an amplifier' d3 which is coupledbetween lthe output circiut of the full-wave rectier 42 and the pair ofdiagonally disposed terminals 31, 3l of the bridge-rectifier circuit.

The transient-modifying signal translating system of the receiverfurther includes means, in the form of a normally closed electron-'tubeswitching means or system in the signal-translating channel, responsiveto the control effect developed by units 4l, r42 and 43 for modifyingthe signal-translating characteristics of the aforesaid channel within ashort interval after the initiation of the transient, whereby the outputsignal of the channel approximately correspends to the applied signalwith modified transients. This means comprises the diodes 21, 28, 32 and33 of the previously described bridge-rectifier circuit.

Operation of transient-modifying signal-transloting system of Fig. 1

The operation of the transient-modifying signal-translating system Ilrepresented in Fig. 1 and the results obtained thereby may be bestunderstood by reference to Fig. 2 of the drawings. Each of the curves ofFig. 2 to be described hereinafter is, exaggerated somewhat for thepurpose of clarity. Curve A of Fig. 2 represents to a very enlargedscale a fragmentary portion of an amplified video-frequency signalsupplied for single line scansion by the output terminals 30, 3@ of thevideo-frequency amplifier l@ to the transient-modifyingsignal-translating system il. At time to a positive-going transient ofthe television video-frequency signal is initiated and terminates attime t3. Following the transient, the video-frequency signal continuesat a substantially uniform positive amplitude level until time tiwhereupon a second and negative-going transient occurs and terminates atapproximately time tv. At approximately time tv another positive-goingtransient is initiated and terminates at time tio, whereupon anadditional negativegoing transient commences and terminates shortlythereafter at time tis. For the purpose of the explanation whichfollows, it will be assumed that the pass-band characteristic of thesignal-translating system of Fig. l including the amplifiers it and I6,when unmodified by the action of units lil-43, inclusive, is incapableof faithfully translating transients steeper than those represented incurve A of Fig. 2.

The differentiating circuit 4I responds to the various ones of thetransients described in the preceding paragraph and, by the well-knowndifferentiating operation, develops an output signal corresponding tocurve B of Fig. 2, The output signal 'of circuit 4! represents the iirstderivative signal of that of curve A and is applied to the full-waverectifier 42 which develops, in the well-known manner, an output signalhaving the Waveform represented by curve C of Fig. 2. It will be seenthat the signal of curve C comprises a unidirectional signal of`positive polarity corresponding to the absolute magnitude of the firstderivative of the signal represented by curve A. The output signal ofthe rectifier :l2 is amplified by the unit 43 and is applied as acontrol potential to the terminals 3l, 3l of the bridge-rectifiercircuit or switching means, and this control potential may also berepresented by curve C. Since the diodes 2l, 28, 32 and 33 are normallymaintained in a conductive state by the battery 35, the controlpotential represented 'by curve C does not exceed the thresholdpotential of the switching system comprising the diodes just mentioneduntil time t1. This control potential is applied by the amplifier 43with positive -polarity to the terminal 3l that is coupled to thejunction of the cathodes of the diodes 32 and 33. Accordingly, at timet1 the control potential from unit 43 is effective .to render each ofthe diodes of the switching system nonconductive, thereby effectivelyopening the signaltranslating channel and interrupting the translationof the video-frequency signal to the input circuit of theimage-reproducing device i8. At time t2 the value of this controlpotential falls below the threshold level, as represented in curve C,and the potential of the battery 35 is again effective to render thediode-switching system conductive, thereby completing the circuit of thesignal-translating channel to the image-reproducing device i8. Theopening and closing operation of the switching system in thesignaltranslating channel is represented by curve D of Fig. 2 of thedrawings. At time t5 the control signal developed by the units 4'l--43,inclusive, exceeds the threshold level of the switching system and thediodes are again rendered nonconductive and remain thereat until time tewhen the con-trol potential drops below the threshold level, thuscausing the switching system to be open during the interval ifs-ts asrepresented by curve D. During the succeeding intervals tis-ts, ta--tirta-etn, and tir-'512, the switching conditions of the diodes appear asshown by curve D for reasons which are clear in View of the previousexplanations given in connection with the control intervals ti-tz,tz-ts, and tista Referring now to curve E of Fig. 2, there isrepresented the waveform of the output potential of thetransient-modifying electrical signal- 'translating system as `appliedto the input terminals 3i, 3l oi the image-reproducing device i3. Itwill be seen that at time to the output potential of the system is zero,corresponding to the zero value of the signal, represented by curve A atthe time to, as it appears across the output terminals 30, 30 of thevideo-frequency amplifier iii. At time t1 the diode-switching system isopen or nonconductive, as shown by curve D, so that no signal thenappears at the terminals 3i, 3i and this condition continues until timet2 whereupon the switching system closes. It will be noted from curve Ethat the potential applied to the terminals 3l, 3| at time t2 rises verysuddenly to -a positive value due to the abrupt closing oi theelectronic switches and also due to the low impedance of the outputcircuit of the arnplier I6, this low impedance enabling the condenser 34to be rcharged very rapidly. Thus the signal translated shortly aftertime t2 to the image-reproducing device corresponds in magnitude withthe signal, represented by curve A shortly after time t2, which isapplied to the output terminals 3i), 30 of the video-frequency amplifierI6. Referring yagain to curve E, it will be seen that thevideo-frequency signal remains at this level until the time te. Althoughthe switching system opens at time t5, as represented in curve D, thecondenser 34 is charged just -prior to that time to `a 'potential levelrepresented by curve E and remains at that value since the charge cannotleak off instantaneously because the discharge path for the condenserthrough the input circuit of the image-reproducing device I 8 has a highimpedance when the switching systeni is open. At time ts the switchingsystem closes and, as will be noted from curve A, the potential appliedto the terminals 3G, Sli becomes substantially zero. Accordingly, thepotential developed across the condenser 34 at time te decreasessuddenly to substantially the zero value, as represented by curve E,because of the low impedance of the discharge path for the condensercomprising the cathode resistor of the cathode-follower amplifier of thevideo-frequency amplifier I6. The switching system remains closed untiltime ts whereupon it is suddenly opened and, since the potential at theterminals 30, 30 was substantially zero during the interval iis-ts, nochange in potential occurs at the terminals 3|, 31|. At time t9 theswitching system closes whereupon the potential developed across thecondenser 34 ycorresponds to that represented by curve A at the vtimet9. At time tn when the switching system again opens, the charge on thecondenser again isr a relatively large' positive value as represented bycurve A so that the potential across the condenser 34 is maintained atthe positive value for the intervaltg-tm- Het ever, a-t time 'tm theelectronic switch suddenly closes and the potential appearing across thecondenser 31S drops 'to substantially zero, as represented in curve E,thereby corresponding in magnitude at that time with the potentiaideveloped across"- the terminals 3c, Sil, may be seen from curve AoiFig. 2. l

Thus it will be seen from the foregoing eX planation that thesignal-translating. channel of the system il norm-ally has'asubstantially linear signal-translating characteristic except forsubstantially the entire portion of each of the oiescribed transients..The translating system is therefore able faithfully to translatevideo-freu quency signals except for substantially the entire intervalci each of the transients, during which intervals thesignal-translatingl channel is disconnected fromthe image-reproducingdevice i8 and hence the channel` is eectively unre sponsive to thetransients. The operation ofthe switching system in the channel is suchthat the i relatively steep unidirectional transients of the typerepresented by curve A of- Fig. 2 are so modied as effectively to formnew or more desirable transients oi the sort shown by curve E and havingslopes which are much steeper than those or" the original transient.These modied transients in turn so control or modify the intensity cithe electron beam of the image-reproducing device it that the imagereproducedl on the uorescent screen thereof has exceptional sharpness.

The balanced arrangement of the bridge-type switching system includingthe: diodes 21,. 2li, 32 and 33 is effective to prevent controlpotentials supplied thereto from the amplifier 43 from appearing in theoutput signalv delivered by the signal-translating channel to therinputcircuit of the image-reproducing device I8.

Although the operation of the transient-modifying system has beenexplained inv connection with the application thereto of a televisionsignal having transients with only relatively steep slopes or generallyrounded edges as represented by curve A of Fig. 2, it may be undesirableto transform all rounded edges of the television signal to steeptransients of the type represented by curve E since gradual variationsin the shading oi the television picture may be wanted in order that thereproduction be accurate. Accordingly, the parameters of thevsignal-translating sys-,em are proportioned sothat the roundedA f edgesof a television` signal transienthavin'g a duration much greater than aselected transient duration are translated. bythe channel withoutdistortion. It willalsobe clear that the threshold bias potentialestablished by the battery 35 in the switching systemA may be so`selected that only those transients which have a derivative exceeding apredetermined amplitude level are effective to overcome thatbias andthereby improve the sharpness ofthe reproduction afforded.

by the image-reproducing device t8.l

*While the transient-modifying signal-translating system has beendescribed with relation to a signal-translating. channel having a band!width corresponding to that present inthe pictureesignal translatingchannel of'a` conventional 10 television receiver, it will be manifestthat a channel having a bandwidth substantially less than that oi aconventional receiver maybe employed with a transient-modifyingsignal-translating system in accordance with the present inventionwithout impairing the sharpness of re'- production oi the televisionpicture. ln the absence of the described units which produce a nonlinearaction in the signal-translating channelduring the interval of atransient, the channel `just mentioned is unable to translate the' veryhigh-frequency components of the transient due to its narrow pass-bandcharacteristic, and therefore the translation by the channel isimpaired. However. the sharpness improvement circuits of the presentinvention associated with the signal-translating channel enable thelatter to translatefto the image-reproducing device l-B a usefulvideo-frequency signal including steep transients so that thereproduced' picture has a sharpness comparable' to that provided by aconventional television receiver although' somewhat limited in detail'.However, this loss in detail is much less annoying' to the observer`than the a' loss ofl sharpness' which results with a conven- Referringnow to Fig'. 3V of the drawings, there is represented' schematicallyanother embodie ment of thev invention which is adapted to be connectedtothe terminals 39, 3c and 3l, 3l of the receiver represented in Fig. 1.The transientmodifying signal-translating system represented in Fig. 3comprises a pair of similar series-con nected units 45 and dii whichform a signal-translating channel` normally' having a substantiallylinear signal-translating characteristic for an ap plied televisionsignal except for at least a portion of aA transient. These unitsinclude a pair of cascaded-coupled oppositely poled rec'tiiier flevicesii andk 48 in the signal-translating channel. These rectifier devicesmay be of the Contact,

- crystal or the'th'err'nionic' type. One' electrode of the rectifierdevic'edfllI is coupled to a terminal` Si! through a coupling condenserit andthe other electrode thereof is coupledto asimilar electrode of thedevice 'i8 through a coupling condenser tii. TheV remaining electrode ofthe device 48 is connected to an output terminal 3|. A series-connectedbattery 52 and a resistor 53 are coupled between the junction of thecondenser de and the rectifier device' el and the other input terminal3b ofthe unit t5. Unit 45 includes simi larly arranged elements 5d and55. The circuit of: unit includes a parallel-connected condenser 5i anda resistor' 58 while unit it includes similarly connected components 59and tt. A series-connected coupling condenser 62 and an inductor iii-iarecoupled` in parallel with the rectiiier device @l while correspondingelements of the unit d6 include a condenser fifi and an inductor E5'.The batteriest2" and 5i are so-poled withl relation to theircorresponding rectier cle--k vices 41' and lili as to maintain them in anormally conductive condition.

Operation of Fig. 3 system the units 45 and iii during the conductiveintervals oi the rectifier devices 'il' andv liB have ay linearsignal-t'ra'nslating'v characteristic andi, in

the' absenceofv a" transient` in the video-frequency acres-se signal,faithfully translate the video-frequency signal between the terminalstil, 3d and 3i, 3i. When the rectifier devices 4l and lil areconductive, they present a very low impedance to a signal translatedthereby. lThus a substantially linear signal-translating path betweenthe terminals just mentioned comprises the condenser 9, the rectierdevice 47, the condenser Et, the rectiiier device 43 and the conductiveconnection between the two lower terminals 3d and 3i. When anegative-going transient is applied to the terminals 3G, 3d and thechange in the amplitude thereof between its first level and its secondlevel occurs at a rapid rate, the potential appearing across thecondenser 5l cannot follow the rapid change of potential of the appliedsignal. Thus a potential related to a derivative of the transient or atime-dinerence signal is developed across the two terminals of therectier device 4l of such polarity as to render that devicenonconductive, thereby interrupting the signal translated to theterminals 3i, Si. Thus the condenser 5l constitutes a control-circuitmeans in the signaltranslating channel of the transient-modifying systemfor developing a control effect related to a derivative of the transientand in the form oi a bias potential for application to the rectifierdevice ll. The biasing of the rectiiier device il to a nonccnductivecondition establishes an oscillatory condition in the circuit comprisingthe inductoi' t3, the condenser 62, the condenser 5l, the resistor 5t,the condenser l and the lowimpedance source coupled to the terminalsEil, Sil. The parameters of the circuit just described are soproportioned that after a short interval of the order oi a half cycle ofthe resonant irequency a potential difference is established across therectifier device di which is eiective to permit the rectier device againto become conductive, thus reclosing that circuit in thesignal-translating channel. Since the rectifier device il is normallyconductive, positiveegoing transients do not cause it to becomenonconductive and are thus translated in a substantially linear manner.The unit [is responds in an inverse manner to unit 15, that is, unit 4tresponds to positivegoing transients in a manner similar to thatexplained in connection with the application of negative-goingtransients to the unit 45, so that further explanation oi its operationis deemed unnecessary. Hence, during the interval in which the rectierdevices are conductive, the system has a linear signal-translatingchannel except for a short interval after the initiation of thetransient when the signal translated by the channel is interrupted. Thusthe operation of the Fig. 3 system corersponds essentially to thatexplained in connection with the graphs of Fig. 2 for the Fig. 1 system.

Description of Figs. 4 cmd 5 embodiments Referring now to Fig. i of thedrawings, there is represented diagrammatically a further embodiment ofthe invention which is suitable for connection between the outputterminals dit, in of the detector and A. G. C. supply l5 and. the inputterminals 3l, 3| of the image-reproducing device I3. A video-frequencyamplifier H and a variable delay network 16 are coupled in cascadebetween the pairs of terminals just mentioned. Coupled between theterminals ill), d@ and an input circuit of the variable delay network'i6 is a control circuit responsive to a derivative of a transientapplied to the terminals just mentioned. This control circuit comprisesa conveni2 tional differentiating circuit 13 and a deiayeontrol system'i4 for controlling the time delay provided by the network to a signalapplied thereto yfrom the unit 'I l', thereby modifying the transientproduced by the described system. The operation o this type of atransient-modifying system will be apparent after a consideration of theembodiment oi the invention represented in Fig. 5.

The schematic circuit diagram or" Fig. 5 represents a specific form ofthe system appearing in Fig. 'e of the drawings. The video-frequencyamplifier 'H is coupled between the terminals et, it and a time-delaynetwork the latter comprising serially connected inductors l2, l2 andshunt-connected condensers le, l0. The remote end of the network le isprovided with an IVI-derived termination It!! which is connected toground through a battery 15. An intermediate point of the network isconnected to the control electrode of a pentode-type electron tube 'ilwhile the two end points of the network are connected to the controlelectrodes of similar tubes 'i8 and i9., respectively. The cathodes ofthese tubes are grounded, the screen electrodes are connected in aconventional manner to a source oi potential indicated as -l-SC, and theanodes are connected together and to one of the output terminals :li andto a source of potential +B through a seriesconnected resistor and apeaking coil i i. Thus the tubes ll, '53, and 'I9 haveparallel-connected space-current paths and comprise electron-tube meanscoupled to the signal-translating channel and to predetermined portionsof the time-delay network it. The battery 'l5 is eiective to provide apredetermined bias potential to the input circuits of the tubes il-l,inclusive.

The differentiating circuit 13' coupled to an output circuit of thevideo-frequency ampliii 'il comprises a transformer 83 having a priwinding de and a center-tapped secondary t ing 85, the mid-point oi thelatter being ground Individual windings of the transformer are conunected in parallel with individual ones of condensers 86, 8l and di)which are shown in broken line construction since they may be comprisedin whole or in part of the distributed capacitance of the windingsassociated therewith. Damping resistors 96, 9i and 92 are connectedacross the individual sections of the transformer to broaden thefrequency-response characteristic thereof. The differentiating circuitle has its constants so proportioned that the circuit in'- cludes aninherent time delay substantially equal to that of the first section ofthe delay network 'I6 which is connected to the control electrode of thetube Ti. If necessary, the differentiating circuit may include aconventional time-delay network (not shown) capable of affording to asignal translated thereby the time delay just men-- tioned. A pair ofrectifier devices 93 Iand 9d, which may be of the contact, crystal orthermionic type, are serially connected but with op posite polarityacross the secondary winding of the transformer 83. The junction of thedevices is connected to ground through a resistor and also is directlyconnected to the suppressor electrode of the tube TI. The otherelectrode of the rectier device @3 is connected through a couplingcondenser 9B to the suppressor electrode ci the tube l'8 while thecorresponding electrode ci the device 94 is connected to thecorresponding electrode of the tube 'I9 through a coupling condenser 91.The suppressor electrodes of the tubes 'i8 and i9 are connected toground through re spective resistors 99 and IUI, each of which is 13arranged in series relation with a battery which is effective normallyto maintain those tubes in a condition of anode-current cutoff. Thepotentials supplied to the tube 11 are such that it is normallyconducting.

Operation of the Fig. system The operation of the Fig. 5transient-modifying signal-translating system may be best understood byreference to the curves of Fig. 6. Each of the curves presently to bedescribed is exaggerated somewhat for the purpose of clarity. Curve A ofFig. 6 represents a fragmentary portion of the television signal appliedto the control electrode of tube 11, which signal includes transientsoccurring in the intervals try-t2 and 15a-t5, this signal havingsubstantially 4the same waveform as the signal applied to thevideo-frequency amplifier 1| but being delayed in time with referencethereto. Curve B of Fig. 6 represents the output signal appearing atterminals 3|, 3|. As previously mentioned, the tubes 18 and 19 arenormally biased to anode-current cutoff so that a television signal notincluding the transients would normally be translated through thevideofrequency amplifier and the rst section of the delay network 16 tothe input circuit of the tube 11. Since the tube 11 is normallyconductive, the output signal is supplied from the anode-cathode circuitthereof to the terminals 3|, 3|.

During the interval irlt2 of the positive-going transient of curve A,however, the differentiating circuit 13 develops a control potential ofpositive polarity for application through the condenser 91 to thesuppressor electrode of the tube 19. Since the center tap of thesecondary winding 85 is grounded, a signal of negative polarity isapplied between the electrode of the rectifier device 93 connected tothe condenser 96 and ground. This control potential renders the device93 conductive and develops a negative potential at the ungroundedterminal of the resistor 95 for application to the suppressor electrodeof the tube 11. This in turn drives the tube 11 toward cutoff. Thecontrol potentials applied to the tubes 11 and 19 have a durationapproximately corresponding to that of the duration ifot2 of thepositive-going transient. Accordingly, only the tube 19 is in such acondition as to translate to the terminals 3|, 3| a signal applied tothe input circuit of the tube from the terminated portion of the delaynetwork 16. The over-all delay afforded by the network 16 may be suchthat it corresponds substantially to one or two times the interval o-t2.Accordingly, at time t2 the signal translated by the network 16, and.particularly the positive-going transient thereof, has not reached theinput circuit of the conducting tube 19 so that the transient does notappear in the output circuit of that tube. At approximately time t2 thepositive control effect on the suppressor electrodeof the tube 19terminates as does also the control effect of negative polarity on thecorresponding electrode of the tube 11. Thus the positive-goingtransient, as it appears at the output terminals 3|, 3| has a steepslope of the type represented during the interval ti-tz of curve B. Thetube 11 thereupon returns to its initial condition while the tube 19again is biased to anodecurrent cutoff by the potential of the battery|90 thus marking the end of the positive-going transient. l i

During the interval tz--ts when the television signal does not include atransient, the signal is again translated from the intermediate point ofthe delay network 16 through the space-current path of the tube 11 tothe input terminals 3|, 3 i. Accordingly, the waveform of the outputsignal appears during this interval as represented by curve B of Fig. 6and thus corresponds substantially with that of the signal representedby curve A during the same interval.

During the interval its-t5 a negative-going transient occurs, asrepresented by curve A, and a positive control potential is appliedthrough the condenser 96 to the suppressor electrode of the tube 19.This potential is effective to overcome the bias afforded by the battery|99, thus rendering the tube conductive during the interval justmentioned. Simultaneously, a negative potential is applied across theseries combination of the device 99 and the resistor 95, therebyrendering the former conductive and developing a negative controlpotential for application to the suppressor electrode of the tube 11.Since a negative control potential is then being applied by thetransformer winding 84 to the suppressor electrode of the tube i9, bothof the tubes 11 and 19 are driven substantially to anode-current cutoffduring the interval ta-tr, of the negative-going transient. Since theinput electrode of the tube 13 is connected to the input terminals ofthe delay network 19, the negative-going transient represented by curveA effectively has already passed the input terminals of the network.Thus, in so far as it affects tube 18, the positive amplitude portion ofthe television signal effectively has terminated at approximately timet3 so that the negative-going transient of the signal applied to thevideo-frequency amplifier has the steep slope represented by curve Bduring the interval ts-ti. It will be clear that the output signal ofcurve B appearing at the 'terminals 3|, 3| is of somewhat shorterduration than the signal represented by curve A which is applied to theinput terminals fill, lil of the system but has much sharper transients.In the manner previously mentioned, these transients are eifective toimprove the sharpness of the picture reproduced by the image-reproducingdevice i3. The fact that curve B has a shorter duration than curve Aindicates that a small geometric distortion is present in the reproducedpicture. This small distortion, which is effective to reduce somewhatthe width of the white areas and Widen the black areas of the reproducedpicture, may be desirable to enhance the apparent contrast of thepicture and to compensate for the finite size of the scanning spotproduced by the image-reproducing device. If desired, this smallgeometric distortion may be reduced by using more complex derivativesignals for application to the suppressor electrodes cf the tubes 11, 18and 19,

It will be clear from the foregoing description and explanation that therecticr devices 93 and 94 and the input circuits of the tubes 11, 18 and19 comprise means responsive to the control potential developed by theunit 13 for varying the transconductance of the tubes just mentionedthereby to modify the time delay afforded by the time-delay network 'i9and the signaltranslat ing characteristic of the signal-translatingchannel between the pairs of terminals 49, 49 and 3 i, 3| within a shortinterval after the initiation of a transient applied to the terminals49, 4G.

From the foregoing descriptions of the various embodiments of theinvention, it will be apparent that the signal-translating systems inaccordn ance with the present invention represent simple and inexpensivesystems for modifying or reconstructing relatively sharp transients toproduce therefrom much steeper transients. It will also be manifest thata transient-modifying signaltranslating system embodying the presentinvention may be utilized in a television receiver to enable it toproduce a very sharp picture. A television -eceiver employing atransient-modifying signal-translating system in accordance with theinvention ig effective to reduce eye fatigue and displeasure ordinarilyexperienced by some observers of television pictures. It will also beclear that a transient-modifying signal-translating system embodying thepresent invention is particularly suited for use in a televisionreceiver having a cathode-ray tube with a relatively large display areasince the system is effective to improve the sharpness of reproductionof the picture produced by the receiver.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and medications may be madetherein without departing from the invention, and it is, therefore,aimed to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and means responsive to said control effect for modifying thesignal-translating characteristic of said channel within a shortinterval after the initia-` tion of said transient, whereby the outputsignal of said channel approximately corresponds to said applied signalwith modified transients.

2. A transient-modifying electrical signaltranslating system for atelevision receiver for translatingr a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and means effectively in said channel responsive to said control effectfor modifying the signaltranslating characteristic of said channelwithin a short interval after the initiation of said transient, wherebythe output signal of said channel .approximately corresponds to saidapplied signal with modified transients.

3. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; differentiating means coupled! to said channel for developing aderivative of said applied signal; control-circuit means coupled to saiddifferentiating means and effectively responsive to said derivative ofsaid transient for developing therefrom a control effect; and means re-16 sponsve to said control effect for modifying the signal-translatingcharacteristic of said channel within a short interval after theinitiation of said transient, whereby the output signal of said channelapproximately corresponds to said applied signal with modied transients.

4. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; differentiating means coupled to said channel for developing aderivative of said applied signal; control-circuit means coupled to saiddifferentiating means for developing from said derivative a controleffect related to the absolute magnitude of said derivative of saidapplied signal; and means responsive to said control effect formodifying the signal-translating characteristic of said channel within ashort interval after the initiation of said transient, whereby theoutput signal of said channel approximately corresponds to said appliedsignal with modified transients.

5i. lA transient-modifying' electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; differentiating means coupled to said channel for developing aderivative of said applied signal; control-circuit means including afull-wave rectifier coupled to said differentiating means for developingfrom said derivative a control effect corresponding to the absolutemagnitude of said derivative of said applied signal; and meansresponsive to said control eifect for modifying the signal-translatingcharacteristic of said channel within a short interval after theinitiation of said transient, whereby the output signal of said channelapproximately corresponds to said applied signal with modifiedtransients.

6. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and switching means in said channel and responsive to said controleffect for modifying the signaltranslating characteristic thereof withina short interval after the initiation of said transient, whereby theoutput signal of said channel approximately corresponds to said appliedsignal with modified transients.

'7. A transient-modifying electrical signal-- translating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel, including a pair of output terminals and anenergy-storage device coupled thereacross, normally having asubstantially linear signal-translating characteristic for an appliedtelevision picture signal; control-circuit means coupled in circuit withsaid channel for developing a control effect related to a derivative ofrsaid transient; and switching means in said channel and responsive tosaid control effect for modifying the signal-translating characteristicthereof within a sho-rt interval after the initiation of said transient,whereby the output signal of said channel approximately corresponds tosaid applied signal with modified transients.

8. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and electron-tube means effectively in said channel and responsive tosaid control effect for modifying the signal-translating characteristicthereof within a short interval after the initiation of said transient,whereby the output Signal of said channel approximately corresponds tosaid applied signal with modified transients.

9. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a

television signal-translating channel, including output terminals and anenergy-storage device coupled thereacross, normally having asubstantially linear signal-translating characteristic for an appliedtelevision picture signal; control-circuit means coupled in circuit withsaid channel for developing a control effect related to a derivative ofsaid transient; and normally closed switching means in said channel andresponsive to said control effect for interrupting the signal translatedlcy said channel thereby modifying the signal-translating characteristicthereof within a short interval after the initiation of said transient,whereby the output signal of said channel approximately corresponds tosaid applied signal with modified transients.

l0. A transient-modifying electrical signaltranslating systemfor atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantiaily linearsignal-translating characteriestic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transientexceeding a predetermined amplitude value; and means responsive to saidcontrol effect for modifying the signal-translating characteristic ofsaid channel within a short interval after the initiation of saidtransient, whereby the output signal of said channel approximatelycorresponds to said applied signal wi'th modified transients.

ll. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to the first derivative of saidtransient; and means responsive to said control effect for modifying thesignal-translating characteristic of said channel within a shortinterval after the initiation of said transient, whereby the outputsignal of said channel approximately corresponds to said applied signalwith modified transients.

12. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and a bridge-rectifier circuit, including a first pair of diagonallydisposed terminals coupled in series relation with said channel and asecond pair of diagonally disposed terminals coupled across saidcontrol-circuit means, responsive to said control effect for modifyingthe signal-translating characteristic of said channel within a shortinterval after the initiation of said transient, whereby the outputsignal of said channel approximately corresponds to said applied signalwith modified transients.

13. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal, said channel having a frequency bandwidth substantially lessthan that of a conventional television receiver signal-translatingchannel so that translation of said transients thereby tends to beimpaired; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;and means responsive to said control effect for modifying thesignal-translating characteristic of said channel within a shortinterval after the initiation'of said transient, whereby the outputsignal of said channel approximately corresponds to said applied signalwith modified transients which are much steeper than said impairedtransients.

14. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means in said channel for developing a controleifect related to a derivative of said transient; and means in said.channel responsive toy said control effect for inodifying thesignal-translating characteristic of said channel Within a shortinterval after the initiation o-f said transient, whereby the outputsignal of said channel approximately corresponds to said applied signalwith modified transients.

l5. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means in said channe1 for developing a controleffect rela-ted to a derivative of said transient; and a pair ofcascade-coupled oppositely poled normally closed means in said channelresponsive to said control effect for modifying the signal-translatingcharacteristic of said channel within a short interval after theinitiation of said transient, whereby the output signal of said channelapproximately corresponds to said applied signal with modifiedtransients.

16. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a. televisionsignal-translating channel, including output terminals and anenergy-storage device coupled thereacross, normally having asubstantially linear signal-translating characteristic for an appliedtelevision picture signal; control-circuit means in said channel fordeveloping a control effect related to a derivative of said transient;normally closed means responsive to said control effect for interruptingthe signal translated by said channel thereby modifying thesignal-translating characteristic of said channel within a shortinterval after the initiation of said transient; and means for reclosingsaid interrupting means after said short interval, whereby the outputsignal of said channel corresponds to said applied signal with modifiedtransients.

1'7. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping at least one control effect related to a derivative of saidtransient; and a time-delay control means coupled to said channel andresponsive to said control effect for modifying the signal-translatingcharacteristie thereof within a short interval after the initiation ofsaid transient, whereby the output signal of said channel approximatelycorresponds to said applied signal with modied transients.

18. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient; atimedelay network coupled tosaid channel; means responsive to saidcontrol effect for con,- trolling the time delay provided by saidnetwork thereby modifying the signal-translating charcteristic of saidchannel within a short interval and 5 after the initiation of saidtransient, whereby the output signal of said channel approximatelycorresponds to said applied signal with modied transients.

19. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;timedelay means coupled to said channel; electrontube means coupled tosaid channel and to predetermined portions of said time-delay means; andmeans responsive to said control effect for varying the transconductanceof said electrontube means thereby modifying the time delay afforded bysaid time-delay means and the signaltranslating characteristic of saidchannel within a short interval after the initiation of said transient,whereby the output signal of said channel approximately corresponds tosaid applied signal with modied transients.

20. A transient-modifying electrical signaltranslating system for atelevision receiver for translating a television picture signal whichmay include unidirectional transients comprising: a televisionsignal-translating channel normally having a substantially linearsignal-translating characteristic for an applied television picturesignal; control-circuit means coupled in circuit with said channel fordeveloping a control effect related to a derivative of said transient;time-delay means coupled to said channel; electron-tube means, havingparallel-connected space-current paths, coupled to said channel and topredetermined portions of said time-delay means; and means responsive tosaid control effect for varying the transconductance of saidelectron-tube means thereby modifying the time delay afforded by saidtime-delay means and the signal-translating characteristic of saidchannel within a short interval after the initiation of said transient,whereby the output signal of said channel approximately corresponds tosaid applied signal with modified transients.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,315,539 Carson Sept. 9, 1919 2,271,876 Seeley Feb. 3, 19422,363,813 Somers Nov. 28, 1944 2,421,138 Wheeler May 27, 1947

